new problem...got caught in the rain... (Electrical?!)

[ERM83]

Just a random fun note: the lady is also trying to get a bike, and is as obsessed with riding as I am. Trying to find her an xs 400 maybe?! Therefore the need to fix this bije. She's tiny, but the first one while on the back of the SG to yell through her helmet "GO #*!@#&? FASTER ON THIS STRETCH!". KEEPER.

[ERM83]

Note on the spark test: the tester light comes on, no problem. Maybe just a bad connection??

[TopCatGr58]

Hey Eric,

Back to basics of testing. Get it running, warmed up, and then spritz water on the header pipes...which ones sizzle, and which ones just drip down the pipe? If you are truly running on 2 cylinders, this will tell you which ones are working/hot and which ones aren't.

IF they are paired 1-4 or 2-3 , then it's electrical....usually. If they are paired 1-2 or 3-4, then it's likely fuel...usually!

If 1-4 or 2-3, then swap both the 1-4 and 2-3 plug wires to opposing cylinders, and then also swap the orange/grey trigger wires as well. Then fire it up and see IF the same cylinders are hot/cold. If the heat moves to the other cylinders....then carbs/engine is working, but the electrical is messed....and the ign Coils are suspect because the TCI and PUs are now working for the previously cold cylinders that are now hot so the PU and TCI are triggering, but the Ign. coil isn't responding.

If same cylinders cold after swap, then it's carbs/engine OR PU coils/TCI, but the Ign. coils are good. And you've tested the PU coils, and swapped TCI, still have cold cylinders, but didn't state which ones and if they stayed the same after the TCI swap?

Can't recall....OEM pipes/mufflers? Take mufflers off and shake to hear anything rattling loose? Try to blow thru the mufflers to see if you can detect any restriction on either side? Cleaned carbs.....use MIKUNI Jets or aftermarket generic?? Vacuum slides working, not sticking, no holes in diaphragms?? Ever do a compression test?

T.C.

[ERM83]

Hey Eric,

Back to basics of testing. Get it running, warmed up, and then spritz water on the header pipes...which ones sizzle, and which ones just drip down the pipe? If you are truly running on 2 cylinders, this will tell you which ones are working/hot and which ones aren't.

IF they are paired 1-4 or 2-3 , then it's electrical....usually. If they are paired 1-2 or 3-4, then it's likely fuel...usually!

If 1-4 or 2-3, then swap both the 1-4 and 2-3 plug wires to opposing cylinders, and then also swap the orange/grey trigger wires as well. Then fire it up and see IF the same cylinders are hot/cold. If the heat moves to the other cylinders....then carbs/engine is working, but the electrical is messed....and the ign Coils are suspect because the TCI and PUs are now working for the previously cold cylinders that are now hot so the PU and TCI are triggering, but the Ign. coil isn't responding.

If same cylinders cold after swap, then it's carbs/engine OR PU coils/TCI, but the Ign. coils are good. And you've tested the PU coils, and swapped TCI, still have cold cylinders, but didn't state which ones and if they stayed the same after the TCI swap?

Can't recall....OEM pipes/mufflers? Take mufflers off and shake to hear anything rattling loose? Try to blow thru the mufflers to see if you can detect any restriction on either side? Cleaned carbs.....use MIKUNI Jets or aftermarket generic?? Vacuum slides working, not sticking, no holes in diaphragms?? Ever do a compression test?

T.C.

Ok...so, I did the spray test. Cylinder #2 may as well be in my refrigerator...I can touch the header with my hand, no problem. Checked the spark again...I have PLENTY. Checked the plug...it looked fine, but I changed it anyway...still cold. I don't have a clue what the problem could be...I JUST cleaned the absolute crap out of the carbs a couple days ago. NONE of the jets are clogged, or anything. Float levels are near perfect...I actually lowered #2 because it was a bit high, and gas was leaking out from the right intake jet and bottom of the intake mouth. The diaphragms are totally fine, and the slides are golden. The needles/seats are also pristine and are nearly brand new; have perfect spring response. There's definitely compression...I need to get a tester for sure, but just by a hand test, there's no kind of compression leak at all.

All of these symptoms make sense, but at the same time, they DON'T...if that makes sense?! I just can't figure out what the problem is. The spark is there, for sure. Maybe REALLY detail the intake jets?! ALL of the fuel feed jets are clean as a whistle.

I cannot figure this one out...

[vedgar]

no gas

no gas on # 2. Find out why

[TopCatGr58]

Okay,

So now we know it's ONLY 1 cylinder, not 2! Now, time to swap just the spark plug wires on that coil between 2-3, putting the hot #3 wire on #2 and vice versa and start it up again. IF #2 still stays cold, and #3 gets warm, then swap the PLUGS afterwards and restart again, and if stays the same, then you will KNOW that the Coil, wires, plugs are good, and that it's most likely the carb....and associated components.

HOWEVER, if the hot cylinder jumps to the #2, and #3 gets cool, then it's electrical, and could be the plug cap, the wires, or the coil. There's a situation where the coil can not be getting enough voltage so that it develops enough power to fire the first plug, but not enough to go thru the engine and back up the other plug and so you can loose 1 cylinder and it's electrical instead of fuel/mechanical. But that's more likely with the OLD OEM low powered coils, not as likely with the newer high powered coils.

Have you checked the intake boots and their mating to the head? The bolts can loosen, but also the mating surface can dry/crumble and create a vac. leak. I used Yamabond/Threebond when I put my new ones on....or you can add a gasket and sealant. Also the synch port cap...is it hardened and possibly leaking.

Have you checked the #2 carbs throttle shaft seals for vac. leaks?

[vedgar]

basics.

You have spark at #2. It is not getting fuel if the pipe is cold. Pull the plug, Is it wet ? Too much fuel. Is it dry. No fuel. If 1 3 4 are operating and getting hot, forget all the fancy diagnostics and stick to the basics. If the plug is dry pull the vacuum plug test port for # 2 and spritz a little starting fluid in the port and see if it gets #2 excited and running. I will wait for your reply

[BA80]

Do you have the air box off? I always leave it off when I'm doing carbs. It's easier to pull them again if necessary if it's not there.

There are only 3 things a mechanically sound engine needs to work. Air, fuel, and spark.

I haven't read EVERY post in this thread but I've been kinda following. Have you checked valve adjustment and compression. If the valve clearances at in spec and the compression is good you have a mechanically sound engine.

Now, back to the BIG 3.

You say it has spark. Strike that.

If the engine is sound then it HAS to be getting air. If so strike that.

Fuel is ALL that's left. This is where leaving the air box off helps.

Can you spray a little carb cleaner or brakekleen into the throat of that #2 carb and get it to fire when it's running? If so you STILL have a carb issue.

[3Phase]

Idle mixture screws

Erm, you said earlier in the thread that you have the '79 carbs and pod filters on your '80 Special.

On top of everything else, you may have broken tips from the idle mixture screws jammed in an idle port or several. The '80 and later carbs use different screw tips that don't have that problem but that would make one cylinder cold at idle.

It would not cause the engine to lose power when you open the throttle.

[BA80]

Erm, you said earlier in the thread that you have the '79 carbs and pod filters on your '80 Special.

On top of everything else, you may have broken tips from the idle mixture screws jammed in an idle port or several. The '80 and later carbs use different screw tips that don't have that problem but that would make one cylinder cold at idle.

It would not cause the engine to lose power when you open the throttle.

You are exactly right about that Scott. I think I've had to get busted mix screw tips out of every early set of carbs I've had.

The up side is, in my opinion, the early carbs run A LOT better than the late ones.

[3Phase]

I haven't had a chance to really compare the early and late carbs, Greg. My '79 didn't stay running long enough to tell but I've got the good carbs that I rebuilt off of it sealed in a box filled with nitrogen (I wish... :rolleyes) so they don't rust and rot. I have a few sets with busted screw tips and/or wallowed out idle holes that can't really be fixed, not sure why I keep them.

[motoman]

ERM83, if you haven't tried it yet, and it involves only one cyl., you might unscrew that #2 plug cap from wire and cut that wire back a 1/4 inch, screw cap back on and give it a go.

[BA80]

I haven't had a chance to really compare the early and late carbs, Greg. My '79 didn't stay running long enough to tell but I've got the good carbs that I rebuilt off of it sealed in a box filled with nitrogen (I wish... :rolleyes) so they don't rust and rot. I have a few sets with busted screw tips and/or wallowed out idle holes that can't really be fixed, not sure why I keep them.

As long as the IM orifices aren't too big for the screws to seal off they'll work fine Scott. You just have to REALLY adjust them though, not just count turns because they will flow differently at the same settings.

If you don't want those old bodies I'll relieve you of their pesky presence.

[3Phase]

They're thrashed. Whoever tried to remove the busted tips didn't get it right, then got angry and tore up the carbs.

There are still good ones in the sets so that's why I've kept them. It's frustrating because both bad carbs are #2 in the rack so I can't just swap them and make a good set.

[ERM83]

Just went out and messed with it for 3 hours.

- no broken idle screw.

- cleaned out the air jets.

- checked the T connections.

- checked the carb boots for the 84th time.

- put on a new throttle cable.

- put the carbs back on...primed it.



It will not start now. I'm so beyond defeated and pissed off that I'm about to say *&$% it, and get rid of it. I enjoy working on my bikes, but this is just plain ridiculous. I have ZERO IDEA why it won't start now. Makes NO SENSE.